In Theravada, it is a matter of gradually accumulating merit through good deeds, whereas in Mahayana one should emulate the bodhisattva and help others while also striving to reach enlightenment in this lifetime through faith in helpful Buddhist deities. These are the divergent destinies in the two kinds of Buddhism.
Human nature is different between them too. In Theravada, humans are supposed to do good deeds to make merit, but each person is on an individual path to enlightenment. So our attention is on our own progress.
In Mahayana, since we are supposed to be like bodhisattvas, the ideal for human nature is to put off our enlightenment for the sake of others. We must try to awaken the bodhicitta (Buddha Nature) that is dormant inside of others.
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